From Daily Mail (caution: tabloid):
The CDC is urging Americans to cancel their upcoming flights if they are not vaccinated against measles.
The agency has upgraded its health travel warning after discovering the virus – one of the most infectious in the world – is spreading on US airplanes. A previous recommendation that said Americans should ‘consider making alternative travel plans’ if they could not get vaccinated before departing now says travelers should ‘consider postponing their trip.’